1. Field of the Invention
The present invention relates generally to optical fiber amplifiers such as optical fiber lasers. The present invention relates more particularly to optical fiber systems having an optical power head containing an amplifier stage remote from one or more initial amplifier stages.
2. Technical Background
Optical fiber lasers have many attractive properties that make them suitable for various industrial applications. Such properties can include one or more of good beam quality, easy thermal management, compact size, and good efficiency. Fiber lasers are therefore often preferred to conventional types of lasers, such as solid-state and gas lasers. Fiber lasers are able to produce optical output in the several kW range with excellent beam quality. Thus, these lasers can be used for macro-machining applications like welding and cutting of metal. Furthermore, fiber lasers lend themselves for operation with ultra-short pulses by a method of mode-locking, enabling them to be used in micro-machining applications as well.
Multi-stage fiber lasers are able to provide high brightness optical power, near the diffraction limit for the system. But as power increases, so does the physical size, mass, volume and complexity of the laser itself and also that of requisite ancillary equipment such as cooling and electrical power supply. In many applications this volume of equipment can hinder deployment, as space at or near the point of laser use is often limited and/or expensive. In some instances, the environment at the point of use can also be hostile, requiring further bulk and complexity resulting from additional protective equipment such as shielding, hermetic containers, and EMI and ESD protection. Use of an optical fiber to propagate laser output light from a laser device itself to the point of use is generally well known. But this method of beam delivery is not suitable for propagating high brightness or near diffraction limited beams. High brightness, near diffraction limited fiber beam delivery is substantially limited in length by the onset of parasitic physical effects in the beam delivery fiber itself, for example, Brillouin backscattering and Raman wavelength shifting. Accordingly, beam delivery fibers for high power diffraction limited fiber lasers are often limited to about 1 meter in length or less.
Accordingly, there remains a need for optical fiber lasers that can be used to provide high optical power without suffering from the drawbacks or deficiencies of the prior art.